Heat olive oil in a Dutch oven over medium heat; add onion, ½ teaspoon salt, pepper, and red pepper flakes. Cook, stirring occasionally, until softened, about 5 minutes. Add garlic; cook, stirring occasionally, 2 minutes. Add vodka; cook, stirring to release browned bits from bottom of pan. Add tomatoes and tomato paste to pan. Bring to a simmer; reduce heat to medium low. Stir in remaining 1 teaspoon salt; simmer until flavors meld, about 25 minutes. Cook pasta in a pot of boiling salted water until package directions for al dente. Reserve 1 cup pasta water; set aside. Drain pasta in a colander. Remove tomato sauce from heat. Stir cream and ½ cup Parmesan cheese until combined. Add reserved pasta water, ¼ cup at a time, to loosen sauce. Garnish servings with grated Parmesan cheese and herbs.